Electrolytic method and apparatus for the production of metal hydroxide



Oct. 31, 1961 P. s. ROLLER 3,006,826

ELECTROLYTIC METHOD AND APPARATUS FOR THE PRODUCTION OF METAL HYDROXIDE Filed Oct. 8, 1956 5 Sheets-Sheet 1 10 ty/ .4. [a

57A INVENTOR.

Oct. 31, 1961 P. s. ROLLER 3,006,826

ELECTROLYTIC METHOD AND APPARATUS FOR THE PRODUCTION OF METAL HYDROXIDE Filed Oct. 8, 1956 5 Sheets-Sheet 2 Oct. 31, 1961 P. s. ROLLER 3,006,826

ELECTROLYTIC METHOD AND APPARATUS FOR THE PRODUCTION OF METAL HYDROXIDE Filed 0012. 8, 1956 5 Sheets-Sheet 3 IN V EN TOR.

Oct. 31, 1961 P. s. ROLLER ELECTROLYTIC METHOD AND APPARATUS FOR THE PRODUCTION OF METAL HYDROXIDE 5 Sheets-Sheet 5 Filed Oct INVENTOR 1 02/] 5. Roller,

United States Patent 3,006,826 ELECTROLYTIC METHOD AND APPARATUS FOR THE PRODUCTEON 0F METAL HYDROXIDE Paul S. Roller, 4021 9th St. NW., Washington, D.C. Filed Oct. 8, 1956, Ser. No. 615,218 32 Claims. (Cl. 20496) This application is a continuation-in-part of my application Serial No. 200,775, filed December 14, 1950, now abandoned.

This invention relates to an improved electrolytic method and apparatus for the production of metal hydroxide. In particular, it relates to an apparatus and method for the electrolytic production of aluminum or iron hydroxide for employment in processes relating to the purification of aqueous liquids, water in general, and including city water to be utilized after purification, for example, in carbonated beverages.

The production of aluminum or iron hydroxide by electrolyzing water has been confronted with a crucial obstacle which consists in the rapid increase in electrolytic resistance and simultaneous inordinate decrease in the output of metal hydroxide. Because of these detri mental effects, continued operation with the given electrodes entails such increasing power per unit of product and low yields as to become unfeasible.

The increase in electrolytic resistance is invariably accompanied by and related to the formation of deposits, coatings and crusts on the surface of the electrodes. It hs been generally considered that these coatings are derived from sediment and other impurities in the liquid being electrolyzed.

The mechanical prevention and elimination of the deposits, coatings and crusts has in general challenged the investigator in this art. US. Patent 1,139,778, relating to the electrolysis of sewage, discloses paddles between the electrodes to prevent sediment from adhering to the electrode plates. [15. Patent 1,478,714, discloses rigid agitators or scrapers to prevent solid matter in the liquid from accumulating upon the sides of the electrodes and clogging the spaces therebetween.

It has been proven that neither paddles nor agitators will sutfice to prevent deposits from forming on the electrodes or avoid the rapid increase in resistance with time. The effect of paddles or agitators is only to redistribute material that adheres and is insufficient to overcome the forces of adherence. Rigid bars which may serve as scrapers are also unable to avoid electrode coatings. When scraping Within an accumulated deposit, more or less material is by-passed and a residual coating is left on the electrode surface. Another type of scraping such as may involve a direct contact with the electrode surface may be effective initially in removing coatings from the surface. As the metal dissolves, however, the fresh surface is etched and pocked, and because of the resultant rugged contour of a rigid bar is almost at once unable to gain adequate access to the electrode surface. Still further, as the electrode metal is dissolved away during electrolysis, the surface recedes and a gap is formed between the scraper bar and the electrode surface and into this gap, material insinuates itself to produce new coating, so that any initial effectiveness of the scraping thus comes to an end.

It should be noted, too, as a practical consideration, that the frictional forces between a plurality of contacting rigid scraper blades and interposed electrode surfaces, is very great, the power requirements and structural demands being so excessive that contact scraping during electrolysis will be recognized as being uncompetitive and infeasible for the ordinary purposes of water purification.

I have studied this problem, employing for the purpose principally clear water, as well as water containing suspended solids, and generally metal electrodes of aluminum, and have concluded that as regards the formation of the electrode deposits, coatings and crusts, the suspended material in the water is only of secondary importance, and that the essential factor involved is the electrolytically generated metal hydroxide. The latter in the absence of any foreign solid matter is by itself capable of forming a hard crust on the electrodes during electrolysis and while continuously under water. Foreign matter in the water accentuates the metal hydroxide crust; while in the absence of the metal hydroxide, on the other hand, foreign matter of itself generally forms no substantial coating or crust.

I have also observed that, previous to its forming a hard crust, the adhering generated metal hydroxide is soft, comprising, in fact, a substantially transparent and invisible film of hydrous gel on the electrode surface. The softness is progressively lost during electrolysis until finally stiffening and hardening of the gel deposit oc curs. Thus, there is a time sequence involved in the formation of refractory deposits on the electrodes, which consists in an initially soft film becoming hard with continued electrolysis. The principle of my new method therefore is to circumvent the formation of a hard coating or deposit by the timely removal of the progenitor metal hydroxide film while it is in the early and easily eliminated soft gel stage and before it has hardened.

It is to be noted that the generated metal hydroxide does not harden freely under water, but that this effect occurs only when it is in intimate contact with the metal electrode during electrolytic charging of the latter.

Foreign matter in the water, such as clay, organic matter and other suspended material, incorporates itself into the primary soft, metal hydroxide film. The latter then changes from a substantially invisible to an opaque deposit. The rate of hardening of the composite film, and the tenacity and strength of the resultant electrode crust, are comparatively high. Nevertheless, by the application of suitable dispersal means to the adhering mixed film, while it is still in its early soft stages of development, the formation of coatings and crusts on the electrodes may be greatly reduced or substantially be avoided during the electrolytic generation of metal hydroxide. While various dispersal means may be employed, such as those involving vibration, I have found that the most feasible and commercially successful at this time comprises means for wiping the film from the electrode surfaces.

It is therefore a principal object of the invention to provide an improved method for electrolytically generating metal hydroxide whereby the initial current efliciency is maintained over prolonged periods of operation with given electrodes.

Another object is to provide a novel cell or battery apparatus for electrolytically generating metal hydroxide whereby the yield of product remains consistently high during prolonged periods of use.

A further object is to provide an improved electrolytic cell or battery for the production of metal hydroxide, which is particularly adapted for combination with a resilient electrode wiper structure.

Still another object is to provide an improved method and apparatus for the purification of Water whereby the electrolysis of the liquid is carried out over long periods without interruption due to electrode deterioration.

It is also an object of this invention to provide an improved, electrolytically eflicient portable plate assembly.

A still further object is to provide a method for re-ac' tivation of the electrode plates after prolonged genera tion of metal hydroxide.

With these and other objects in view, as will become 7 plate and electrode wiperg.

more apparent as the description proceeds, my invention is embodied in an electrolytic cell or battery'apparatus comprising an inter-connected assembly of electrode plates, an electrodewiper and wiper assembly coordinated therewith, a drive mechanism for the wiper assembly, and, certain other novel features of construction, combination and arrangement of parts, as will hereinafter be described and claimed.

'For a complete understanding of my invention, reference is to;b'e had to the following description and accompanying drawings, in which:

- .FIG. l is a top plan view of an electrolytic cell in accordance'twith the present invention, the cover being removed totshow the internal assembly; 7

FIG. 2 is a vertical cross-sectional view of the structure shown in FIG. 1; V 7

; FIG. 3 is. a perspective cross-sectional view of a portionof the cell shown in FIGS. l and 2;

FIG. 4 is an enlarged vertical cross-sectionalview of the electrode plate assembly; p Y 7 FIG. 5 is a front elevation of "a pair ofalternate electrode plates; r r V a FIG. 6 is a fragmentary front view of an electrode FIG. 7 is a fragmentary front view of an electrode plate and a modified electrodewiper;

FIG. 8.is across-sectional view transversely through another modified form of an electrode 'wiper member;

FIG- 9 is a cross sectionalview of a modified cell structure;

FIG. 10 is a cross-sectional view taken on line 10,10

of FIG. 9;

FIG. 11 is' an enlarged fragmentary cross-sectional view taken on line 1111 of FIG. 10; FIG. 12 is a cross-sectional view transversely through a modified electrode wiper, and FIG. 13 is a view in elevation of a modified wiper unit. Referring now specifically to the drawings, a cell 10, comprising a plurality of spaced parallel electrode plates or sheets 11, 11' respectively of opposite polarity, is con tained in box ,or case 12, having a cover 13, a liquid or water inlet conduit 14 and a liquid or water outlet conduit 15. The cell 10 is supported above floor 16 of case 12 by resting on the lower extremeties of non-conducting end-panels 17, 17 which may be in the form of strips or plates. Cross-rods 21, attached by nuts 22 to endpanels 17, 17'-at their upper ends, above the stop edges of electrode plates 11, 11', may be provided to serve 1 as handles for cell'10 as a removable assembly, whereby the cell may be manipulated and portably lifted for installing in or removing from the case 12. Cross-rods 23, attached by nuts 24, to end-panels 17, 17 at their lower ends below the bottom edges .of electrode plates 11, 11' may be provided for additional buttressing of the cell10.'--

Wiper structure 25 comprises a plurality of wiper arms 26 individually positioned between adjacent plates .11 and 11'.of cell 10.' Thewiper arms 26 generally are in the shape of laths with the flat side facing the surfaces of electrode plates 11mm 11. Wiper arms 26 consist on their outer part of a flexible or resilient surfacing or covering material 26b which is compressed against'the adjacent electrode plates 11 and 11, and is in continuous elastic contact with the surfaces of the electrodes as these recede due to dissolution of the'electrode metal. The resilient material 26b may be exceedingly yielding, in view oftthe soft character of the adhering generated metal hydroxide gel which is to be wiped from the surfaces of the electrodes. Wiper arms 26 also embody an internal rigid or stiff member 26a supporting the outer yielding, resilient material 26b, the rigidity and stiffness provided by member 26a permitting a reciprocating traction and pulsion of wiper arms 26 against the surfaces of electrode plates 11, 11' without rupture or excessive bending and deformation of the wiper arms. However,

in view of the slight degree of frictional contact between the said Wiper arms 26 and said electrode plates 11, 11, the traction and pulsion is small, and the structural strength of wiper arms 26 generally need not be great.

One construction of wiper arm 26, as shown in FIG.

6, comprises a stiff blade-like center 26a which may be of thin metal or plastic to which is attached on the outer surface a resilient cover 26b such as a resilient covering or protuberance of soft rubber, sponge rubber, foam rubber, sponge cellulosic material, thermoplastic material, and the like. The cover or protuberance 26b may be attached to the said center 26a by cementing, dip coating or electro-deposition. Another construction of wiper arm 26, shown in- FIG. 8, comprises the blade-like center 2611 and a resilient, but exceedingly yielding overlay 260 in the form of a sleeve, tube or hollow membrane which is filled with fluid, namely air in the dry state or liquid electrolyte during electrolytic use. A very soft overlay 260 is particularly desirable where there are many arms 26, and the traction and pulsion therefore tends to be great. The overlay cover 26c consists, for example,tof a thin rubber, rubber-like or thermoplastic resilient sleeve or hollow membrane touching the said blade-like member 26a at the narrow edges and being separated from most of the surface thereof by an air film. The resilience of the sleeve may be increased by spring means embedded within or enclosed by the sleeve. Compression of the membrane 260 takes place against the backing of liquid electrolyte and'is easily effected, so that the frictional contact with the surfaces of the electrode plates 11, 11' is slight although sufiicient to wipe away the soft gel film. Upon compression, sleeve 26c tends to break away from the narrow edges of center blade 26a, and during forced motion of the latter, it may bedragged by the blade 26a.

Wiper arms 26 project beneath and above electrode plates 11, 11', and are consolidated so as to move together by means of transverse rods 47 and 47 passing through holes 46 and 46' respectively in the projecting upper and lower ends of said wiper arms 26. Drive-rods 28 and 28' engage the transverse rods 47 and 47' through detachable yokes 27 and 27' by connection at joints 30 and 30 on yoke rods 31 and 31' of the yokes 27 and 27. The joint 30 may be any suitable fixed connection such as a bolt and nut, or eye and set-screw fastening; the joint 30 may be a latch joint wherein yoke rod 27' rests in an upward-facing notch or notch means, 32 situated in, or supported by drive-rod 28'. The notch means 32 may include a retractable or pawl-like construction to facilitate engagement. In virtue of the latch character of joint 30', the yoke rod 27' and drive-rod 28' may be securely linked, despite the lack of direct access, simply by properly positioning the drive-rod 28 with respect to the yoke rod 27' and then slipping the yoke rod 27' into notch 32.

Transverse rods 47 and 47' are connected to yoke rods 31 and 31' by yoke bands 48 and 48. The transverse rods 47 and 47' pass through holes 57 in yoke bands 48 and 48' while .piercing holes 46 in wiper arms 26, and yoke rods 31 and 31 pass through holes 58 in the yoke bands 48 and 48 while piercing holes 46' in the wiper arms 26. Set screws 59 hold the yoke bands 48 and 48' rigidly to the yoke rods 31 and 31'. Set screws 68 hold the yoke bands 48 and 48' rigidly to transverse rods 48 and 48'. The free connections provided byfholes 57 and 58 in yoke bands 48, 48 permit of an unconstrained, proper positioning of the yoke bands on transverse rods 47 and 47 and on yoke rods 31 and 31', prior to tightening of the set screws 59 and 60. V Drive-rods 28 and 28 pass through stufiing boxes 29 and 29' in wall 18 of battery box 12,,and are attached to cross-bars 33 at the fixed eye-bolt joints 34 and 34. Stops 35 are mounted onthe drive-rods 28 and 28' in order. to limit the travelof wiper structure 25 at both,

ends of the reciprocating stroke, and may, for example, consist of suitable collars locked with set-screws or the like. Cross-bar 33 may be actuated manually in pushpull motion, to provide a back-and-forth sweep of wiper arms 26 across electrode plates 11, 11'. The manual force may be direct, or it may be efiected through a suitable toggle or rack and pinion means.

The wiper structure 25 may be power driven, for example, by an electric motor 35 controlling an eccentric 36, to which an eccentric arm 37 is attached at a slotted joint 36'. At its other end, eccentric arm 37 is connected by a pivotal joint 38 to a crank rod 39 which is connected by a knuckle joint 40 to cross-bar 33. Reduction gear unit 41, for retarding the reciprocating motion to a suitable level, is connected to motor 35 by shaft 42 and to eccentric 36 by shaft 44. The proper initial setting of the stroke of drive-rods 28 and 28' may be effected by the positioning of eye-bolt joints 34 and 34' lengthwise on the drive-rods, while the proper distance of the stroke may be efiected by the radial adjustment of arm 37 in the slotted joint 36.

In certain instances, particularly that of a small cell with wide spacings between the electrode plates 11, 11', or where wide spacings are critically provided, simple modifications may be efiected whereby the yokes 27 and 27 are dispensed with, and transverse rods 47 and 47' then serve in place of yoke rods 31 and 31'.

The structure of cell is particularly adapted for mounting the wiper structure 25 therein, and embodies for this and other useful purposes the features of high internal rigidity, compactness, portability, and a permanently low resistance constant due to the provision of fluid-tight electrical contacts at each of the plurality of electrode plates 11, 11. Electrode plates 11 have two or more pairs of unequal openings 49 and 51), positioned adjacent the lateral margins of said plates, While plates 11 likewise have two or more pairs of unequal openings 49 and 59' identical in size respectively to openings 49 and 50, but positioned in alternate or opposite relation thereto. Electrode plates 11 and 11' are stacked in alternate sequence in the assembly of cell such that openings 49 and 50, and openings 49' and 50, are in successive alignment.

Electrode plates 11, 11 and end-panels 17, 17 are held together in spaced, rigid assembly by the threaded conducting tie-rods 52, 52, metallic spacers 55, 55, and insulating washers 56. The spacers 55 are threaded on tie-rods 52 and make a fluid-tight screw pressure contact with tie-rods 52 and with plates 11 on the plate area just beyond the margin of the small openings 50; similarly, metallic spacers 55 are threaded on tie-rods 52 and make fluid-tight contact with plates 11' on the area beyond the margin of small openings 50. Adjacent the end-panels 17, 17 on the inner side thereof are threaded half-spacers 55a, 55a substituting for spacers 55, 55. Insulating washers 56 fit snugly on spacers 55, 55', 55a and 55a and provide support to the electrode plates 11, 11' on the area beyond the margin of large openings 49, 49'. The assembly of cell 10 is completed by nuts 53, 53' which are threaded on the ends of tie-rods 52, 52' against end-panels 17, 17'.

Electric lead 54, entering box 12 through insulating bushing 57A, is electrically connected with tie-rod 52 and provides current of one polarity through tie-rod 52 to electrode plates 11, while electric lead 54 entering through insulating bushing 57A provides current of opposite polarity to tie-rods 52' and electrode plates 11.

The series of electrode plates 11, 11 are maintained exactly equidistant, and generally in very close separation, by spacers 55, 55 and 55a, 55a. In virtue of the threaded character of the said spacers 55, 55' and 55a, 55a and the tie-rods 52, 52', a high degree of internal rigidity is gained which is adequate for withstanding internal stresses set up by the reciprocating motion of the Wiper arms 26.

Electrode plates 11 may be of one metal such as steel, while electrode plates 11' may be of another metal such as aluminum, or both may be of the same metal. Conrosion during electrolysis tends rapidly to impair the electrical connections to the said plates. In the instance of the spacers 55, 55 being slidably mounted on tie-rods 52, 52', no matter how close the fit, liquid tends to insinuate itself therebetween, producing an electrolytic oxide film on the contact surfaces, which results in a very high electrical resistance to current flow. This short-coming is overcome by the threaded pressure connections between the said spacers 55, 55', tie-rods 52, 52 and electrode plates 11, 11', bonding them in fluid-tight connection and providing permanently low contact resistance.

Electrode wiper arm 26 may take the form of a narrow rectangle as shown in H6. 6. Notches 61 may be situated in the sides of wiper arm 26, as shown in FIG. 7, whereby the wiper arm may extend beyond washers 56 to that part of the surface of plates 11, 11' which is subtended by the said washers. A wiping is thereby desirably provided for the portion of the surface of plates 11, 11' which is otherwise not reached by the wiper arm 26.

After cell It) has been assembled, wiper structure 25 may be mounted into it by inserting wiper arms 25 between each pair of electrode plates 11 and 11', and then attaching transverse rods 47 and 47' and yokes 27 and 27. Cell 10, in combination with wiper structure 25, may then be lifted by the cross-rods 21, and introduced into box 12. The emplacement is done in such manner that yoke rod 31' fits into notch 32 of drive-rod 2'3. Drive-rod 28 is then pushed forward to engage yoke rod 31 at joint 36.

The wiper arms 26 may be reciprotoated continuously or intermittently, either during the electrolysis, or in between electrolytic operating periods, but in any case with sufiicient timeliness to forestall any substantial hardening and thickening of the originally soft metal hydroxide gel fihn.

In an alternate and preferred mode of construction shown in FIGS. 9-12, the cell comprises an assembly of plates 111 and 111', of opposite polarity respectively, housed in case 112. The latter is similar to case 12, and is provided with insulated studs 157A and 1573 for electrolytic power leads to cell 116- 'and with inlet 114 and outlet 115 for water or other electrolyte. Rotary electrode wipers are positioned between adjacent electrode plates 111 and 111' and are removably splined on a centrally disposed rotating shaft 128, Said shaft, driven by motor 35 through reduction gear box 41 and output shaft 44 with coupling 41a, passes through bearing stufiing box 29 at one end and is supported in hearing cage 29a at the other end.

Electrode wiper 125 comprises blade-like or rod-like arms 126a and hub 127. While two arms 126a are shown extending from opposite sides of hub 127, only one such arm or more than two arms may be employed if desired. Arms 126a are preferably offset from the axis of hub 127 so that during rotation, for example clockwise in FIG. 10, the sleeve-like wiper elements 126s are subject to a force component inward whereby they are retained on said arms 126a. Conveniently, the arms 126a and hub 127 are stamped as a unit from relatively thin metal, the hub having a square opening for freely mating with a shaft 128 of square section.

Electrode wiping element 1260 is in the form of a resilient cylindrical tube or sleeve, substantially the same as element 260. Like the latter in its relation to rigid arm 26a, resilient element 1260 fits lightly over a rigid member 126a, being separated from the latter at all points except along the edges. Tube 1260 extends from the end of arm 126a to the periphery of hub 127. The outer surface of tube 1260 makes contact with the walls of adjacent plates 111 and -111' and is compressed between these walls whereby it assumes a flattened elliptic shape about arm 1261:.

Tube 126a is of thin wall, highly elastic rubber, having least permanent set under continuous compression between the plates, and being preferably gum rubber or latex rubber. It may alternately comprise a very thin, metal spring, hollow member 1260', overlaid with thin insulating rubber or plastic material 126a". Hollow member 126c' may be tubular or of a split or open ended hollow form as required.

The structure of electrode plates 111 and 111 include a central aperture 62 which allows passage of shaft 128 through the succession of said plates of cell 110. Each plate moreover is provided with small openings 150 and large openings 149, alternately positioned adjacent the periphery of the plate and preferably at the corners thereof. The larger openings 149 are provided with insulating bushings 65 inserted flush with the plate side walls.

Plates 111 and 111' may be coated with any suitable surface coating 63, such as a vinyl or rubber base paint around its edges and also extending over a limited area subtending each corner while omitting a small area 150 surrounding openings 150. The margin of coating 63 at the corner coincides approximately with the furthermost reach of wiper arm 126a during its rotational traverse in the neighborhood of the corner. Coating 63 serves a two-fold useful purpose; it prevents the accumulation of excess metal hydroxide at such areas which are not reached by wiper arm 126a during its rotary motion, and it protects the edges of the plates from selective dissolution and incipient crack formation.

In a typical assembly of plates 111 and 111' to form cell 110, insulating washer 156 and spacer nut 15-5, placed one against the other, are at all times interposed between said plates in such manner that said insulating washer lies against the margin surrounding bushed opening 149 and the said spacer 'nut lies against the area 150 surrounding opening 150 to make contact with the plate. An insulating sleeve 70 is desirably placed around each spacer nut 155 whereby concentrated currents which may act on the proximate surfaces of plates 111 or 111' are avoided. Screw-threaded tie-rods 152 and 152 pass successively through an opening 150, spacer nut 155, in sulating washer 156, and insulating bushing or tube 65 in opening 149, ad seriatim. In virtue of the construction as set forth, tie-rod 152 makes electrical contact with plates 111 while tie-rod 152 makes electrical contact with electrode plates 11-1,

The assembly of plates may be terminated by foot supports 117 and 117', making electrical contact respectively with tie-rods 152 and 152' through the appropriate use of insulating bushings 65 in said foot supports. An insulated non-dissolving metal plate, for example of stainless steel or a non-conducting plate, for example of rigid plastic, may be interposed in any suit-able manner between the foot support 117 or 117' and the terminal electrode plate 111 or 111 of the cell assembly to buttress said terminal plate against the stresses of the electrode plate wipers 125. Terminal post 69 may be afiixed to foot support 117 and terminal post 69' to foot support 117 for connection to electrical leads from insulated studs 157A and 157B respectively, whereby the plates 11 1 receive current of one polarity and the plates 111 receive current of the opposite polarity.

The cell assembly as hereinabove described has certain distinctive advantages. It is noted that each plate 111 or 111' is held tightly between two spacer nuts 155 at each of the four corners, thereby providing a rigid cell structure capable of withstanding lateral pressures and shears due to wiping. In addition the intercalation in every instance of insulating washer 156 and spacer nut 155, and nothing more or less between each pair of plates 111 and 111', provides in a simple manner for a constant, highly accurate, spacing of all said plates.

was being actively generated by the electrodes.

, the surface.

It has been found that in some instances the surfaces of the electrode plates may be pitted or otherwise roughened and, in such instances, the wipers are incapable of removing the gel from the depressed areas because of their smooth surfaces. In such cases, a modified wiper unit as shown in FIG. 13, may be efifectively employed. This unit may be similar to the unit 125 except that additionally it is provided with brush or like member 126d, one such member being disposed in tandem with each Wiper element 31260 in the illustrated embodiment. The member 126d preferably comprises bristle, filamentous, or finger-like elements which are sufficiently tough and stiff but resilient to penetrate the depressed areas of the plate surface and dislodge the soft gel therefrom, and preferably these elements are non-conducting, nylon or like thermoplastics or rubber being highly suitable materials from which the elements may be formed.

Brush member 126d may also be employed without wiper element 1260, more particularly in the instance that the bristles of member 126d are closely spaced in multiple files. 7

By inclusion of wiping of the electrodes as hereinbefore described, certain new and highly useful results have been obtained in practice, including greater currents, greater yields of metal hydroxide, and prolonged electrolysis without excessive deterioration of the electrodes. As an example, the average of results may be taken that were obtained in the electrolysis of city water in which electrodes of aluminum alloy were employed, with and without wiping of the said electrodes. In each instance, at a potential of 7 volts, the current initially was about 30 ma./sq. in. In ordinary electrolysis without wiping of the electrodes, the current dropped continuously; at the end of about 24 hours the current value was about 8 ma./sq. in., and the generation .of metal hydroxide was slight; With electrolysis in which the electrodes were wiped recurrently every hour, the current decreased slowly during about the first hour and then remained practically constant. After 24 hours the current value was about 22 ma./sq. in., or almost three times as great as without wiping, and metal hydroxide The twenty-four hour yield of metal hydroxide was about four times as great with the wiping as described than without wiping.

The appearance of the electrodes differed markedly in the two cases. The electrodes that were not wiped were in part moderately coated and in part covered with tenacious crusts, consisting essentially of aluminum hydroxide, that had formed on the electrodes under the water and were present during electrolysis. On the other hand, the electrodes for which the periodic wiping had been employed, were substantially smooth and had only a spotty film on the surface.

The higher the voltage drop across the electrodes the more rapidly the gel film tends to form and harden on Also, when foreign impurities are present in the water, hardening of the gel film takes place at an accelerated rate. In this and similar instances, a particularly efiicient, and frequent or continuous, wiping of the electrodes during use may be required. To the extent that this requirement is not fulfilled, and in general if wiping is too infrequent, toughened films or coatings may accrue on the electrodes with time.

Due to this condition, an increased electrical resistance is entailed, although generally electrolysis may be continued at satisfactory current and output values with the given electrodes as they are. Nevertheless, if so desired, the film may be removed and the electrodes readily renewed by treatment with a chemical solution.

.However, with a heavily coated and crusted electrode as obtained in the absence of wiping, an additional step 'prior' to chemical treatment is preferred. This consists in scraping away of the hard deposit overlaying the electrode, which is both inconvenient and costly.

The invention contemplates re-activation of electrode plates which have become coated with the hardened gel, as in the event that wiping of the plates as hereinabove described is imperfectly executed or in the event of a developed ruggedness or roughness of the plates with comcomitant depressions therein that are not efficiently reached by the wiper elements. The reactivation step is indicated whenever the voltage in the course of electrolytic generation has increased excessively with an appreciable diminution in the yield of metal hydroxide. It comprises subjecting the cell to a solution which is capable of dissolving the hardened gel film from the electrodes, specifically an acid solution containing an inhibitor, and preferably while the plates are being wiped as hereinabove described, but with the electrolytic current off.

For purpose of re-activation I prefer a weak acid solution containing an inhibitor against dissolution of the metal comprising the electrode plates. Such inhibited acid solutions are per se well known in the cleaning art and are not claimed as such but only in a new and useful combination with electrolytic generation of metal hydroxide, and especially with Wiping of the electrode plates as hereinabove described. Examples of suitable acids and inhibitors with respect to aluminum and steel, the principle electrode metals contemplated in the invention, are set forth by Eldredge and Mears, Industrial and Engineering Chemistry, volume 37, pp. 736-41 (1945). The acid which I prefer for re-activation is muriatic acid at a concentration of from about 0.05% to 3% containing an inhibitor at a concentration of about .0l% to 0.2%. For inhibitor I prefer hexamethylene tetramine, but have also successfully employed thiourea. It is evident that practically any of the inhibitors listed by Eldredge and Mears will be suitable. I have also successfully employed phosphoric acid containing sodium chromate for. re-activation.

As an example of the use of re-activation solution but Without being necessarily limited thereto, aluminum electrodes in flowing tap water were employed for the generation of aluminum hydroxide for coagulation purification of the water in conjunction with a filter. The polarity of the plates was periodically reversed. During electrolytic generation, Wiping of the plates was carried out as hereinabove described at a mean rate of 1 inch per minute. The initial voltage was 4.5 volts at an electrolytic current of 2.25 amps. After 43 hours the voltage had risen to an average value of 8.7 volts. At this point the electrolytic generation was stopped, and the water was replaced by a solution of 2% muriatic acid containing 0.15% hexamethylene tetramine. The cells were subjected to this solution for 30 minutes. Thereupon the solution was drained and the battery rinsed twice with water. The voltage now dropped to its original value of 4.5 volts and the battery responded thereafter exactly as in new condition. The amount of aluminum metal dissolved was quite negligible.

Another significant benefit obtained by wiping of the electrodes as described consists in the improved mechanical durability of the wiped electrodes. With the ordinary electrolysis, the metallic structure of the electrode usually disintegrates and flakes of metal are to be found interspersed with the metal hydroxide. This electrode disintegration occurs most rapidly when the electrolysis is carried out persistently against the rising electrical resistance, and is particularly marked for coated and crusted electrodes. On the contrary, electrodes to which wiping has been applied during electrolysis retain satisfactorily their structural integrity and strength.

In the purification of water, the liquid after being discharged from battery case 12 may enter a separator of suspended matter such as a coagulation and sedimentation tank system, or may pass directly to a filter. In either case, my new method of wiping the electrodes during electrolysis is advantageous in maintaining a consistently low power requirement and greatly prolonging the useful life of the electrodes in the purification process.

It will be understood that I do not wish to limit myself to the exact construction and arrangement of parts shown, as it is obvious that various changes in details may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. The method of electrolytically producing metal hydroxide from metal electrodes and an aqueous liquid nonsolvent to said metal hydroxide comprising introducing the liquid into a case containing a plurality of said metal hydroxide-producing electrodes, passing electrolyzing current across said electrodes, during electrolysis passing resilient elements over the surfaces of said electrodes to thereby remove from the surfaces an electrode-generated, soft gel-like metal hydroxide film prior to its hardening on the surfaces whereby a deposit thereon including crusts formed from the soft film is prevented and re sultant scraping for removal of said deposit is avoided, and discharging the liquid containing metal hydroxide from the said case.

2. The method of electrolytically producing metal hydroxide from metal electrodes and an aqueous liquid nonsolvent to said metal hydroxide comprising introducing the liquid into a case containing a plurality of metal hydroxide-generating electrodes, passing electrolyzing current across said electrodes, passing flexible elements across and against the surfaces of said electrodes during electrolysis to thereby displace from the surfaces irrespective of the degree of electrode dissolution an electrodegenerated adhering, soft, gel-like metal hydroxide film before it hardens on the surfaces whereby a deposit thereon containing the soft film in hardened form is prevented vand resultant scraping for removal of said deposit is avoided, and discharging the liquid containing metal hydroxide from the said case.

3. In the purification of water by the electrolytic generation of insoluble metal hydroxide therein from metal electrodes, the steps comprising introducing the water into a plurality of charged electrodes of said metal, mechanically wiping said electrodes by the light pressure of flexible surface-contacting elements which follow the metal hydroxide-generating surfaces of the electrodes to displace therefrom adhering, generated metal hydroxide in its early, soft formation and prior to its hmdening on the surfaces. in a surrounding soft deposit, and discharging the water containing generated metal hydroxide into a separator of suspended matter.

4. In the purification of water for beverage use by the electrolytic generation of aluminum hydroxide therein, the steps comprising adding drinking Water to a battery of hydroxide-generating aluminum electrode plates, electrically charging the plates, mechanically wiping the plates by the light rubbing action of a resilient electrodecontacting element to remove adhering, generated aluminum hydroxide while the latter is gelatinous and soft and before it has hardened and crusted within an associated deposit, and discharging the Water containing generated aluminum hydroxide from the battery into a filter.

5. An electrolytic battery apparatus for generating metal hydroxide comprising a battery case, liquid inlet and outlet means connected to said battery case, an assembly of metal hydroxide-generating electrodes mounted in said battery case, electrical conducting means connected to said electrode plates, a plurality of wiper arms situated between said electrodes, mounting means to support said wiper arms, resilient fluid-filled thin hollow members on said wiper arms extending outward therefrom and bearing continuously against the surfaces of said electrodes in elastic relationship thereto, and drive means attached to said mounting means for moving said resilient members over and against said electrodes whereby electrode generated, soft, gelatinous metal hydroxide is disward therefrom and bearing against said electrode plates,

mounting means supporting said wiper arms between said electrode plates, and drive means attached to said mounting means for reciprocating said wiper arms, across said electrode plates whereby generated, soft, gelatinous metal hydroxide is displaced from the electrode plates and a low electrode resistance is maintained.

7. An electrolytic battery apparatus for generating aluminum hydroxide comprising a battery case, water inlet and outlet conduits to said battery case, an assembly of interconnected aluminum electrode plates in said battery case, charging means for said electrode plates, a plurality of wiper arms situated between said electrode plates, thin and resilient fluid-filled sleeve-like members on' said wiper arms in frictional contact with the surfaces of the said electrode plates, mounting means for said wiper arms, and drive means connected to said mounting means for moving said wiper arms across the surfaces of the said electrode plates.

8. An electrolytic battery for generating metal hydroxide comprising a plurality of parallel metal hydroxideproducing electrodes, insulating end-pieces for supporting said electrodes, pairs of large, and small'openings in the marginal portions of said electrodes, the said electrodes being alternately positioned to provide an alignment of said large and small openings, threaded conductor tie-rods passing through the aligned openings in said electrodes and through aligned openings in said endpieces, threaded metallic spacers between said electrodes threaded on said tie-rods and bearing in fluid-tight relationship against each alternate electrode on the electrode area beyond the margin of said small openings, insulating washers on said spacers abutting each adjacent electrode on the area beyond the margin of said large openings, nut tightening means threaded on the ends of said tie-rods bearing against said end-pieces, electrical connection means on said conductor tie-rods to provide charges of opposite polarity to each of said alternately positioned plates, a plurality of membrane-like wiping elements situated between said electrodes and flexed against them, and mounting means for said elements arranged to reciprocate them across said electrodes.

9. An electrolytic battery for generating metal hydroxide comprising a plurality of parallel metal hydroxidegenerating electrodes, insulating end-pieces for supporting said electrodes, pairs of large and small openings on the margins of said electrodes, the said electrodes being alternately positioned to effect an alignment of said large and small openings, threaded conductor tie-rods passing through the aligned openings in said electrodes and through aligned openings in said end-pieces, threaded metallic spacers between said electrodes threaded on said tie-rods and bearing in fluid-tight relationship against each alternate electrode on the area beyond the margin of said small openings, insulating washers on said spacers abutting each adjacent electrode on the area beyond the margin of said large openings, nut tightening means threaded on the ends of said tie-rods bearing against said end-pieces, electrical connection means on said conductor tie-rods to provide charges of opposite polarity to each of said alternately positioned plates, cross-rods connecting said end-pieces above the top edgesof said electrodes to provide handles for manipulating the plurality of said electrodes, a plurality of membrane-like wiping elements situated between said electrodes and flexed against them,

12 and mounting means for said elements arranged to reciprocate them across said electrodes.

10. An electrolytic battery structure comprising a plurality of spaced metal hydroxide-generating electrode plates, aligned openings through the margin of said plates, conductor tie-rods extending through said aligned openings, metallic spacers alternately contacting said tie-rods and said electrode plates, insulating means'alternately interposed between said tie-rods and said electrode plates, and thin flexible wiper members extending toward and against said electrode plates adapted to contact and reciprocate over the surfaces of said spaced electrode plates for the removal therefrom of electrode-generated soft metal hydroxide gel before it hardens and forms a crust 'in an enveloping deposit on said electrode plates.

' 11. An electrolytic apparatus for generating metal hydroxide comprising a battery case, liquid inlet and outlet conduits to said battery case, a plurality of metal hydroxide-generating electrodes in said battery case, insulating end-pieces supporting the said electrodes above the floor of said battery case, pairs of large and small openings on the margins of said electrodes, the said electrodes being alternately arranged to effect an alignment of said large and small openings, threaded conductor tie-rods passing through the aligned openings in said electrodes and through aligned openings in said end-pieces, threaded metallic spacers between said electrodes threaded on said tie-rods and bearing in fluid-tight relationship against each alternate electrode on the area beyond the margin of said small openings, insulating washers on said spacers abutting each adjacent electrode on the area beyond the margin of said large openings, nut tightening means threaded on the ends of said tie-rods bearing against said end-pieces, electrical connection means on said conductor tie-rods to provide charges of opposite polarity to each of said alternately positioned plates, cross-rods connecting said end-pieces above-the top edges of said electrodes to provide handles for manipulating the plurality of said electrodes, a plurality of r'nembrane-like wiping elements situated between said electrodes and flexed against them, and mounting means for said elements arranged to reciprocate them across said electrodes.

-12. In the purification of water by the electrolytic generation of insoluble metal hydroxide therein, the steps comprising adding Water to a battery of hydroxide-gen crating metal electrodes, mechanically wiping the electrodes during electrolysis by the light rubbing action of a flexible electrode-contacting element to displace an adhering electrode-generated metal hydroxide film while the latter is gelatinous and soft and before it has solidi- .fied and hardened a soft coating, and discharging the water containing generated metal hydroxide from the battery into a separator for suspended matter.

13. The method of electrolytically generating insoluble metal hydroxide comprising the steps of maintaing metal hydroxide-producing electrodes immersed in an electrolyte which is non-solvent to said metal hydroxide, maintaining an electrolyticpmetal hydroxide-generating current passing to said electrodes, wiping the metal electrodes during electrolysis to remove an electrode-generated, gellike soft film of metal hydroxide, before hardening and encrusting of the film and formation of an accumulation containing said hardened film, by the light rubbing actrion of a flexible, compressed element passingover the metal hydroxide-producing surface of the said metal electrodes, and continuing the electrolytic generation of metal hydroxide.

14. In the method of producing insoluble metal hydroxide, the steps of generating metal hydroxide electrolytically in an electrolyte which is non-solvent to said metal hydroxide and displacing from the metal electrodes electrode-generated soft films of gel-like metal hydroxide by the light rubbing action during electrolysis ofa soft, flexible, electrode-surface contacting element, whereby hardening and crusting of: the gel and formation of a 13 coating containing said hardened gel on the electrode surface is avoided.

15. In producing electrolytic insoluble metal hydroxide with consumable metal anodes and water, the method of prolonging the electrolytic useful life of the anodes which comprises electrolytically producing free metal hydroxide within the body of the water while generating a thin, soft, gel film on the surface of the anodes and removing by resilient anode-contacting means the thin, soft, gel film from the surface of the anodes before it has become transformed into an irreversible hard coating on the said surface, whereby the surface is rendered free of accumulations requiring scraping for their removal.

16. An electrolytic battery for generating insoluble metal hydroxide comprising a plurality of electrode plates, a receptacle therefor, current means connected to said plates, substantially rigid members situated between said plates but not in contact therewith, a resilient fluidfilled hollow membrane on each of said members extending outward therefrom and making wiping contact with each of said adjacent plates, and means to move said members across said plates during the electrolysis.

17. An electrolytic battery for generating insoluble metal hydroxide comprising a plurality of electrode plates, a receptacle therefor, current means connected to said plates, flat, substantially rigid members situated between said plates but not in contact therewith, a resilient, fluidfil'led tubular material attached to said fiat member, said material extending away from said member toward said plates and making Wiping contact therewith, and means to move said members across said plates during the electrolysis.

18. An electrolytic battery for generating insoluble metal hydroxide comprising a plurality of electrode plates, a receptacle therefor, current means connected to said plates, inter-plate connections at the margins of said plates whereby alternate plates are of opposite polarity during electrolysis, flat, substantially rigid members situated between said plates but not in contact therewith, said members provided with notches at the edges subtending said interplate connections, a resilient, thin material attached to each said flat member, said material extending away from said member toward said plates and making wiping contact therewith, and means to move said members across said plates during the electrolysis.

19. An electrolytic apparatus according to claim wherein said mounting means rotatably supports said wiper arms.

20. An electrolytic apparatus according to claim 5 wherein said mounting means reciprocally supports said wiper arms.

21. An electrolytic apparatus according to claim 5 wherein the resilient members each comprise a rubber tube.

22. An electrolytic apparatus according to claim 5 wherein the resilient members each comprise a brushlike element.

23. An electrolytic apparatus according to claim 5 wherein the resilient members each comprise a thin, spring metal hollow member and an insulating cover thereover.

24. An electrolytic apparatus according to claim 5 including a brush-like element in tandem relation to each wiper arm.

25. An electrolytic apparatus according to claim 5 wherein the member on each said wiper arm comprises a resilient plastic element.

26. An electrolytic cell comprising a plurality of alernate parallel electrode plates, said plates provided at the border with alternate large and small openings, an insulating tube inserted in said large openings substantially flush with the plate surfaces, an insulating washer disposed at either end of said tube, a metal spacer nut between alternate said plates and disposed in such manner that it lies against said insulating washer and against the portion of the adjacent plate surrounding said opening, screw-threaded tie-rods passing in succession through said small opening, spacer nut, insulating washer, insulating tube in said large opening, another insulating washer and another insulating nut, nuts on the ends of said tierods whereby the terminal electrode plates are held in the assembly, flexible means situated between adjacent said plates for displacing a soft, gel film on the surface of said plates before it has hardened and crusted, and means for moving said flexible means over the surfaces of said plates.

27. A cell according to claim 26 wherein an insulating layer is provided over said spacer nut.

28. A cell according to claim 26 wherein the margin of said plates and a limited area subtending each corner of said plates is provided with an insulating layer.

29. In the electrolytic generation of metal hydroxide from a cell of metal electrode plates and an aqueous liquid non-solvent to the metal hydroxide, the steps of electrolytically generating metal hydroxide, a portion of which resides as a soft gel film on the surfaces of the plates, displacing the major port-ion of the film during the generation and before it has hardened and crusted, after a substantial rise in resistance subjecting the plates to a weak solution of an acid containing an inhibitor against metal dissolution, and resuming electrolytic generation.

30. In the electrolytic generation of metal hydroxide from a cell of metal electrode plates and an aqueous liquid non-solvent to the metal hydroxide, the steps of electrolytically generating metal hydroxide, a portion of which resides as a soft gel film on the surfaces of the plates, displacing the major portion of the film during the generation and before it has hardened and crusted, after a substantial rise in resistance subjecting the plates to a weak solution of an acid containing an inhibitor against metal dissolution, wiping the surfaces of the plates while subjected to said solution until all residual film is removed, and resuming electrolytic generation.

31. An electrolytic cell for generating insoluble metal hydroxide, comprising an assembly of electrode metal plates, a housing enclosing said plate assembly and for containing an aqueous electrolyte non-solvent to the metal hydroxide, an electrode wiper interposed between adjacent said plates and including -a rigid support provided with electrode wiping means contacting the adjacent surfaces of said plates, and means for moving said wipers transverse said plates to cause said wiping means to wipe the surfaces of the plates to remove therefrom an electrode-generated while it is resident on said plates in a soft gel-like condition and before it becomes hardened and crusted, said wiping means being resiliently expansible to follow and maintain contact with the surfaces of said plates as the plates progressively become thinner during the electrolytic generation due to the formation therefrom of metal hydroxide released into the electrolyte.

32. An electrolytic cell for generating metal hydroxide, comprising a housing, an assembly of electrode metal plates in said housing, each of said plates having a central aperture with the apertures aligned in said assembly, a shaft extending through said apertures, electrode wipers interposed between adjacent said plates and each including a rigid support having shaft engagement means drivingly connected with said shaft, resilient electrode wiping means carried by said support and contacting the surfaces of each of said plates, and driving means connected with said shaft for moving said wiping means over the plate surfaces during the electrolytic generation.

References Cited in the file of this patent UNITED STATES PATENTS 857,277 Harris June 18, 1907 1,139,778 Laudreth May 18, 1915 (Other references on following page) 16 v V FOREIGN PATENTS r V 1,161 Great Britain 'o1.1sss

H OTHER REFERENCES V L Metallic Corrosion Passivity and Protection, by

Evans (1948), publ. by Edward Arnold & Co., London; p. 264pertinent. I 5

Great Britain Feb. 27, 1922 

1. THE METHOD OF ELECTROLYTICALLY PRODUCING METAL HYDROXIDE FROM METAL ELECTRODES AND AN AQUEOUS LIQUID NONSOLVENT TO SAID METAL HYDROXIDE COMPRISING INTRODUCING THE LIQUID INTO A CASE CONTAINING A PLURALITY OF SAID METAL HYDROXIDE-PRODUCING ELECTRODES, PASSING ELECTROLYZING CURRENT ACROSS SAID ELECTRODES, DURING ELECTROLYSIS PASSING RESILIENT ELEMENTS OVER THE SURFACES OF SAID ELECTRODES TO THEREBY REMOVE FROM THE SURFACES AN ELECTRODE-GENERATED, SOFT GEL-LIKE METAL HYDROXIDE FILM PRIOR TO ITS HARDENING ON THE SURFACES WHEREBY A DEPOSIT THEREON INCLUDING CRUSTS FORMED FROM THE SOFT FILM IS PREVENTED AND RESULTANT SCRAPING FOR REMOVAL OF SAID DEPOSIT IS AVOIDED, AND DISCHARGING THE LIQUID CONTAINING METAL HYDROXIDE FROM THE SAID CASE. 